The present invention relates to lateral displacement shock absorbing material. The present invention relates to a new way to attenuate impacts using tubular structures having non-uniform wall cross-sections placed at an angle to the direction of impact.
The objective achieved through operation of an impact attenuating material is absorption and dissipation of energy. This is accomplished when one object impacts another by slowing down the movement of the first object in a controlled manner. During the process of energy absorption, the impact attenuating material is compressed.
The degree of impact absorption achievable by an impact attenuating material is directly related to the difference between the pre-impact thickness and the thickness of the material when compressed to the maximum degree. Impact absorbing materials known in the prior art such as expanded polystyrene, expanded polypropylene, air bladders, and others bottom out when the input energy exceeds the ability of the impact absorbing material to further deform or crush. When the material bottoms out, further compression does not occur and, once bottoming out occurs, all of the further benefits of impact attenuation are gone.
For example, in the case of a material having a nominal pre-impact thickness of one inch, the material bottoms out with a thickness of 0.35 inches. Thus, only 0.65 inches of the material or 65% of it participate in the attenuation process. The remaining distance (0.35 inches) consists of the material stacking up and getting in its own way.
The science concerning use of impact attenuating materials to absorb energy is well known. Generally speaking, by varying the density and thickness of any given impact attenuating material, differing amounts of energy are capable of being absorbed. The challenge facing designers of impact attenuating products is to appropriately balance the criteria of thickness, stiffness, and energy absorbing characteristics of a product so that the product is effective structurally, cost effective, as well as commercially viable. Thus, for example, numerous impact attenuating materials might be effective in attenuating impacts on an athlete wearing a helmet. However, if the initial thickness of the impact attenuating material is too high, this requires the helmet to be made with an outer shell that is too large in dimensions to be commercially viable regardless of the price or efficiency of impact attenuation.
Generally speaking, consumers demand relatively smaller and lighter products. Thus, in an athletic helmet, it is important to conform the outer shell of the helmet as closely as possible to the head of the athlete.
Helmet designers typically attempt to design a helmet that will reduce the risk of a broad range of injuries from mild traumatic brain injury (MTBI) to death, and for use in a wide range of activities such as from baseball to lacrosse to football to motor sports. The designers attempt to anticipate the kinds of impact energies that are most likely to occur and to design the helmet to preclude or at least minimize the likelihood of serious injuries from such impacts. The challenge in designing such a helmet is, again, to manufacture the helmet in a size that most optimally conforms to the size of the head that is to be protected thereby. Helmet designs are necessarily a compromise. Impact attenuation is tuned to absorb the type of energy that is most likely to result in permanent or catastrophic injury as a result of a specific activity. Thus, for example, motorcycle helmets are made extremely stiff because they are tuned to attenuate high energy impacts that result from road crashes. By contrast, football helmets are designed “softer” because they are tuned to the energy that results from players colliding together.
To achieve the combination of attenuation of both life threatening and non-life threatening energy levels, a helmet would have to be 1.5 to 2 times the thickness of one that was designed to only protect from life threatening events. A helmet designed to protect a user from MTBI events and not intended to address higher life threatening energies would be thin, but would be seen as unacceptable to the user because it would not adequately reduce the risk of catastrophic injury or death.
In order to achieve a broad range of input energies, the impact attenuating material must be made extremely thick. If a helmet designer chooses to design a helmet intended to absorb high energy impacts, a high density material would be used. If the same designer desired to achieve low energy absorption, a low density material would be employed. If the designer intended to achieve high and low energy absorption, thick materials would be required. All of these parameters and criteria are factored together and a suitable compromise is achieved for each intended activity and the required protection from impacts that typically occur when engaged in such activity.